This application proposes to continue the study of human aggressive responding under controlled laboratory conditions. The research will go into important new directions. The external validity of the laboratory model of human aggression will be evaluated by selecting two very similar populations with and without documented histories of violence. An additional experiment will establish the relationship between a history of substance abuse/dependence and aggressive responding among adult subjects. These two experiments, will for the first time involve testing of female subjects. In addition to laboratory measures of aggressive responding, we will also be taking additional measures to compare violent versus nonviolent and substance abuse history versus no substance use history. These measures will include the following: (1) a laboratory measure of impulsiveness, which will use operant procedures designed to measure self- control behavior, (2) psychometric measures of aggression, anger and impulsiveness, and (3) a biochemical measure of serotonergic activity which will involve measuring prolactin following the administration of a challenging drug, buspirone. The laboratory measures of impulsiveness were included to attempt to correlate measures of impulsiveness and aggressiveness in these different populations. The psychometric measures have been included to provide an independent measure of aggression/hostility and impulsiveness which can be compared to the laboratory measures. The prolactin measures of serotonergic activity were included because of all the recent research linking diminished serotonergic activity with animal and human aggression, and with impulsive behaviors in humans. In these studies we will develop a behavioral, psychometric and biochemical profile which we hypothesize will be related to histories of violence and histories of substance dependence. Such profiles will identify individuals who may be at high risk for developing substance dependence problems. In addition, we are proposing to continue our drug research on the effects of marijuana and cocaine on human aggressive responding. We will extend these studies to determine how the effects of marijuana and cocaine on aggressive responding may be altered by the level or frequency of provocation. We will also assess the effects of repeated cocaine administrations on aggressive and escape responding. We will compare these effects male and female subjects for the first time. These studies will also be important to the development of the laboratory study of human aggressive behavior and other aspects of human behavior. Establishing external validity of the laboratory model and an association with substance abuse, will lead to studies of other subject populations, to possible targeting of at risk populations, to evaluations of treatment techniques and assessment of social response probabilities and possible predictions of such behaviors in the "real world".